Depends on what I want. If I want a certain something, like a full breed dog, then I am going to go with a breeder. As these dogs are often more expensive, they have to be something I REALLY want and I am going to set guidelines for what I want and do my research. Like Ari, my Sheltie. She came from a breeder, and I had very specific requirements in what I wanted. Color other than Merle was important, and look(as I thought I might be interested in trying out showing) was VERY important to me. And since I was considering trying out showing registration was another of my requirements. As Ari is just over a year old, I am kind of sorry I spayed her, as she is turning out to be a GORGEOUS dog. A friend of ours who shows dogs says she has perfect ears(which I took care and time to glue and set). Her two major flaws are 1) she is kind of nervous around people and I don't think would set up well for a judge. 2) she toes out very slightly. Not noticeable unless you are looking for it, but she does it all the time.
If I am looking for a good "anything" dog, then I will hit the shelters. I know what "type" of dog I get along with and usually I can pick out the mutts that work best for me. Collie/Shepherd mixes have been the best dogs for us, and whenever we go to the shelters in search of a dog, we always keep an eye out for that kind of cross. We also set requirements for those dogs and often go to several shelters in the area before settling on one.
Basil is my rescue dog. I got him from the shelter as a six month old(my perfect age. I hate puppies. Too much work). He was a black lab mix, which I don't really like labs, as all the full breed labs we'd had in the past have been hideously stupid and died in hideously stupid ways. No running in front of cars for those guys. But there was something about him(looked like border collie), and I had to have him. I went to two different shelters after seeing him and then went back and got him.
There are great things to be said about full breed dogs and shelter dogs. Right now my family(same area, different locations) have nine full breed, registered, dogs(five pugs, a sheltie, two dobermans, and a min pin) and three mixed farm dogs. Surprisingly the fullbreeds outweigh the mixed. It is usually the other way around.
If you are going to pay through the nose for a dogs from a breeder, set your standards high and get your money's worth. Get the best dog you can for the standard of the breed you are looking for, and have it registered through a reputable breed organization, like the AKC in the US. Even if you don't show or compete, take pride in the breed and make your dog into a good example of the breed. I paid WAY too much for Ari, but she hasn't let me down yet. She is just what I wanted.
If you are going to go through a shelter, set your standards high and get your hearts worth. Make the right choice for you, your family and the dog.
Under normal dog-searching circumstances, I go through the shelters. They are 'cheap', there is a great number of options, they are one of a kind(in jest I often call Basil my 'custom made' designer dog. Made just for me), and generally, from all the ones we have adopted, they are extremely loyal. They know where they came from, and thank you in thier own way.
Here are Ari and Basil. My darlings.